Tamper evident closures (TEC's) are designed to provide some evidence of unauthorized opening of any contained goods such as tablets. Traditionally these containers are produced with a closure cap and tamper evident means to hold various consumer products whereby a potential user of the container can tell if the container has already been opened or unsealed. Typically these types of containers are used to hold medicines in tablet form and the container and tamper evident closure are formed from a polymer plastics material by an injection moulding technique process or by a thermoforming process. There are also many other types of containers that use or need TEC's as well as tablet containers.
A TEC is formed including a cap with a thread and catching or locking means and a removable tamper evident ring joined to the cap by discrete piece(s) of frangible plastics or bridge members. Any such ring also has protrusions on an inner side which are designed to interact with the containers thread or neck catching means, whereby the action of twisting the cap (say anticlockwise) off to open the container, causes the cap protrusions to engage the catching means on the container to break the bridge member whereby the ring from the cap is left behind on the container thread or neck.
The action of the ‘catching’ can be done in many different ways such as by ratchet type protrusions or teeth over container pawl segments or by protrusions or rim protrusions catching a circular rim. However these methods of catching or locking are reliant on complicated injection mould tooling and maintenance to ensure the integrity of the catching. Some methods of manufacture have at least two unrelated steps that must be carried out. For example in a first step i.e. a moulding step, there is the moulding of the cap and ring in a mould in one step which can only be done having outwardly protruding protrusions or teeth and then, in a completely separate and different step, folding the ring inwardly with respect to the cap, to cause the protrusion/teeth to be located inwardly as required to lock with an external thread or neck of a container where there is the potential for the folded inward ring or teeth to fold itself outward as the cap is being removed failing to indicate that the cap has been tampered with.
This moulding step is carried out generally because it is the most efficient way to mould teeth or protrusions so that they allow one easy step to eject the moulded cap and ring out of the mould without destroying the ring and teeth. Also the folding step is difficult to carry out correctly and so must be done with precision. Another problem with this type of one step moulding is that with a worn mould or incorrect mould setup, where there is too much injection pressure used, there is a tendency for the plastic to flash across the discrete piece(s) or frangible bridge members, in effect this causes the ring that is to break away from the cap to be joined as part of the cap and can not break off so the TEC looses the ability to show that the cap has been removed.
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